This movie is exactly as good as you think it will be.
Remember how you were wondering how they could pull off such an ambitious movie like the Avengers and then they did some how? Well that, but again, and it is still excellent.
(this review gets a little into details, but nothing really spoilery)
When Tony Stark, a man who thinks he is justified to do anything in the name of protection shockingly goes too far and creates Ultron, a murder bot who loves murder. Ultron, who is basically evil Tony, is very quippy. But this being a Whedon flick, everyone seems really quippy (don't worry, it's not as annoying as that sounds).
One of the best things about this movie is the destruction that you see happening in the action scenes. Something about the other Marvel movies never really made the people seem in danger when everything was exploding, but there are people everywhere in these scenes, screaming in horror as the super people punch the murder robots. Many innocent bystanders die in this one. Easy. Some of the other movies just seem too "clean", no sense of danger.
I also really liked the characters in this one. The other Marvel movies always seem like maybe one or two supporting characters from the other movies show up, but this movie has so many people in it. All your favourites!
Also, it had a really great "adventure continues" vibe. This movie starts with Avengers action and ends with Avengers action. There is no more "how they came together" or "this changes the very foundation of the universe". It was an awesome addition to what is now a serial story. More of this and less of origin stories!
So in conclusion, check out this sweet indie Whedon film, you might not have heard of it but it's pretty cool.
